1. Field of the Invention
The present invention relates generally to an electronic control device associated with an internal combustion engine, and more particularly to an electronic control device which responds to at least two work parameters of an internal combustion engine.
2. Description of the Prior Art
Customarily, motor vehicles having internal combustion engines are equipped with controls which respond to various work parameters of the engines. Such controls usually function in such a manner that a sensor monitors a work parameter when the engine is running, and an indication of the parameter is either shown in a continuous display Or otherwise. In the usual case, there is only one display occurring in response to the work parameter exceeding a given threshold value. Internal combustion engines are commonly provided with a warning light that goes on when the oil pressure reaches an unacceptable low value. Furthermore, it has been common practice in motor vehicles having water-cooled internal combustion engines to provide an indicator for the cooling water temperature. For this purpose, a sensor is used to measure the cooling water temperature which is generally displayed by way of an analog display instrument. In a large number of motor vehicles, the temperature sensor is connected with a thermostat which activates a fan to further assist the cooling water control mechanism.
The engine temperature and the cooling water temperature are parameters which can only be changed very slowly over a long period of time. Therefore, the possibility exists that the exceeding of a given maximum temperature can take place unnoticed, due to the fact that the driver cannot detect or pay attention to a steady increase in the temperature. As a result of this situation, there is the possibility of irreparable damage to the engine after a long period of operation at unacceptably high temperatures, even though the excess over the threshold value for the cooled water temperature or the engine temperature was correctly indicated.
Another possible cause for the unnoticed passing of a permissible threshold value of a work parameter in an internal combustion engine, especially in today's motor vehicles, is the fact that the vehicle operator is under intense stress resulting from heavy traffic for long periods of time, and cannot pay attention to the indicators on the dashboard. Furthermore, the operator of a motor vehicle can be in a special situation, such as driving through a construction site on an expressway, or having to encounter many traffic lights and a variety of traffic signs which may expose the driver to a high level of irritation, resulting in the driver's not paying attention to the optical indicators on the dashboard.
There is a further possibility that a standard thermostat for measuring cooling water temperature may break down, leading to a simultaneous failure of the cooling water temperature indicator. In such a case, the exceeding of the permissible threshold temperature is not shown, which can also lead to damage to the engine.